Many prefabricated structures are now being utilized in the construction industry. Such structures are typically assembled at a remote manufacturing facility and then transported to the job site for incorporation into the building. The use of prefabricated structures can result in substantial cost savings by decreasing the amount of time and labor required to complete a project. In addition, such structures are generally more lightweight and efficiently engineered than their on-site assembled counterparts.
Prefabricated trussed rafters for use as roof or floor supports are examples of components which are widely used today. Such trusses are assembled from precut wooden chord and web members positioned in abutting relationship and connected together.
Although trusses of this type can be fabricated by hand on a production line basis, several truss assembly machines have been developed for performing this task semi-automatically. In general, the precut wooden members are positioned manually over a support surface and clamped in place, after which toothed fastener plates are laid over or under the abutting joints. The fastener plates are then pressed into the wooden members to secure the joints on one side, after which the semi-complete truss is turned over and similarly secured at the joints on the opposite side.
Various arrangements of tables and press rollers have been employed in the truss assembly devices of the prior art. One approach has been to pass the truss with its support surface and clamps through a pair of press rollers or under a roller mounted on the floor between two table sections. Another approach has been to provide a traveling press which is supported on the floor for travel along a table and across the truss positioned thereon.
The prior truss assembly machines, however, have several shortcomings. Because the relationship between the press roller and truss is critical to successful operation of such machines, slight variations in the floor surface can cause improper connection of or damage to a truss. The prior machines have therefore required extremely flat floor surfaces and frequent maintenance for adjusting alignment. Other machines are adapted for assembling only roof trusses or floor trusses, but not both types at the same time. The capabilities of these machines are somewhat limited. Heretofore there has not been available a truss assembly machine in which the camber to be set in the truss can be adjusted conveniently and positively. The clamping mechanisms utilized by the prior machines have also been found inadequate in terms of adjustability, positive actuation and the like. In addition, the prior machines have been relatively slow in operation because wasteful motion by the workmen has been necessary.
There is thus a need for a new and improved truss assembly machine.